Photon counting systems for breast imaging

We have developed silicon (Si) strip photon counting detectors for modalities used in clinical breast imaging including mammography, tomosynthesis, computed tomography, and lump imaging in the operating room. Typically, x-ray integrating detectors based on scintillating cesium iodide CsI(Tl) or amorphous selenium (a-Se) are used in most commercial systems. Recently, mammography instrumentation has been introduced based on photon counting silicon Si strip detectors with two adjustable energy discriminators for dual energy data acquisition with two contiguous energy windows. The systems presented here use four discriminators for up to four contiguous energy windows or two energy windows with separated upper and lower bounds. The high resolution detectors with 100 micron pixels produce a maximum output count rate of 100 Mcps/mm 2 which is linear up to 40 Mcps/mm 2 and a FWHM energy resolution of 2 keV which is uniform from the noise floor of 4 keV to the upper bound on the dynamic range at 60 keV. The Si strip detectors are packaged into modules which are tiled in different geometries for the different modalities used in breast imaging. We describe the detector optimization and the development of application specific integrated readout electronics that provide the required spatial resolution, low noise, high count rate, and dynamic range for each modality. We present results from prototype mammography, computed tomography, and lump imaging systems as well as describe methods for the absolute quantification of iodine concentration.